Every time electrical current is to be passed from one part of an apparatus to another, separate part, some form of contact unit is needed. Probably the most well known type of electrical contact includes a base from which two or three elongated, parallel, electrically conductive pins extend. The pins constitute male contacts which mate with female contacts. Such contacts are used in most common household machines, the female contacts being located in a wall socket.
It is not necessary for a contact unit to have male contacts in the shape of protruding pins. Electronic circuit boards which are to be mounted in, e.g., computers, are often provided with narrow, parallel contact surfaces. These contact surfaces are arranged along one edge of the circuit board, the part of the printed circuit on which the contact surfaces are provided itself forming a male member, which is inserted in a contact unit which forms a female member and which is mounted on the inside of the casing of the computer.
The aforesaid types of contacts presuppose that the male member of the contact unit is guided generally in a straight line when inserting it into the female member. The direction in which it is guided is the same as the longitudinal direction of the elongated pins or the contact surfaces. It is not possible to use such types of contacts if the male member, when it is brought into contact with the female member, must move in a direction which is not parallel to the longitudinal direction of the male member. Transverse motion of contact units provided with fixedly mounted pins is not even possible, and transverse motion of the aforesaid contact surfaces on a circuit board can cause the surfaces to be damaged or even torn off.
In many modern system cameras it is necessary to convey electric current between the camera housing and removable parts, such as a lens, which are to be mounted on the housing. If the lens is removable it and the camera housing must be provided with some form of electrical contact arrangement. The lens is usually mounted on the camera housing using some rotational motion, and the contact arrangement must be such that it can accommodate this motion.
One way to solve this problem is to arrange sliding contacts in the lens mounting. Such contacts are, however, subjected to friction every time the lens is mounted and this causes increased wear. This usually prohibits the use of precious metals, for example, gold plating of contact surfaces. It is furthermore necessary to insure that the contact surfaces are kept clean.
A more satisfactory arrangement of the contact unit can be achieved by mounting the lens using a locking ring. In this case it is not necessary for the lens itself to be rotated, but rather it may be mounted by holding it against the camera housing while the locking ring is turned. Such a solution makes it possible to convey electric current by means of pins, which constitute male contacts, and which are provided on the camera housing; corresponding female contacts are, in this case, provided on the lens. However, such an arrangement requires the user to be very careful when mounting the lens in order to avoid damaging the pins, especially if there are several pins. It is furthermore not possible to mount other types of lenses without risking damage to the pins.
The object of the present invention is to provide an electrical contact unit by means of which the aforesaid disadvantages may be eliminated.